1. Field of the Invention
The present invention relates to an optical apparatus configured to control manual focusing (“MF”).
2. Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 05-241060 discloses a method for changing a slope in a relationship between a variation amount of a rotating angle per a predetermined time period of a manual focusing ring used for the MF and a moving speed of a focus lens before and after a threshold of the variation amount of the rotating angle and for making the slope at a position equal to or higher than the threshold larger than that than at a position lower than the threshold. However, the relationship between the variation amount of the rotating angle and the moving speed is linear both in a range of the position equal to or higher than the threshold, and in a range of the position lower than the threshold.
JP 05-002204 discloses power focusing configured to change a ratio or (the rotating speed of the manual focusing ring)/(the moving speed of the focus lens) in accordance with a magnitude of the rotating speed of the focus lens, and to set the moving speed of the focus lens. The ratio may be (the rotating amount of the manual focusing ring)/(the moving amount of the focus lens). For example, assume that V0 is the rotating speed of the manual focusing ring, V is the moving speed of the focus lens, VH and VL are two thresholds, and tV is an arbitrary value. Then, JP 05-002204 sets V so as to satisfy V0/V<tv when V0>VH, V0/V=tV when VH>V0>VL, and V0/V>tV when VL>V0.
JP 05-241060 has a problem of a bad operability because when the focus lens is rotated near the threshold, the gain frequently varies, the radical accelerations and decelerations of the focus lens frequently occur. According to JP 05-002204, V becomes discontinuous at V0=VL and at V0=VH in a graph in which the rotating speed V0 is set to the abscissa axis and the moving speed V is set to the ordinate axis, because V>V0/tV when V0>VH, V=V0/tV when VH>V0>VL, and V<V0/tV when VL>V0. As a result, similar to JP 05-241060, the operability degrades near the threshold.
In addition, when a photographer provides finer MF by enlarging the display magnification of the display unit configured to display an image, a conventional variation amount of the focus lens is large and it is thus difficult to provide a fine adjustment.